Health Risks

Cyanobacteria are found around the world living in all surface waters (lakes, ponds, rivers, and streams). They naturally emit toxins as a defense to predators. These toxins can be found in high concentrations when cyanobacteria are very abundant or are released after they die. Exposure to these toxins can impact human and animal health. Health reactions vary depending on the toxin concentrations in the water, the pathway of exposure, and previous health status of patient.

Do not enter or limit your exposure to waters with posted advisories issued by state agencies.

Human Health Risks
The DPH uses a table to decide which recreational activities pose the most risk to exposure of cyanotoxins (Figure 4). Short-term and long-term exposure to these toxins can lead to adverse health effects.

In summary, the more direct contact someone has with the water during a cyanobacteria bloom, the higher the possible risk of exposure to their toxins. If you are someone that enjoys these recreational activities especially in summer months, your level of exposure is something to keep in mind. To learn more about when these blooms may occur please look at our Cyanobacteria, FAQspage.

Take extra precaution if you suffer from: liver disease, kidney disease, cancer, asthma or other lung ailments, or are immunocompromised.

Concern for Domestic Pets, Livestock, and Wildlife
Animals can also suffer from the harmful effects of toxic cyanobacteria blooms. In fact, Lake Champlain in Vermont had such bad algal blooms in the summers of 1999 and 2000 that two dogs died from ingesting the cyanotoxins in the water. The precautions are similar for human and domestic animals. For more information on animal safety please visit the CDC's Animal Safety Alert document. Some of the resources above also have animal health information.

Treatment Options When Exposed to Waters Experiencing a Bloom
Recommendations from the CDC:

Rinse off skin and pets with fresh water as soon as possible, do not let pets lick cyanobacteria off their fur.

If you or your pet swallow water with a bloom, call your doctor, Poison Center, or a veterinarian.

Call a veterinarian if your animal shows any of the following symptoms of cyanobacteria poisoning: loss of appetite, loss of energy, vomiting, stumbling and falling, foaming at the mouth, diarrhea, convulsions, excessive drooling, tremors and seizures, or any other unexplained sickness after being in contact with water.

Fish Consumption Advisory
Fish caught in waters that have experienced recent blooms can accumulate toxins in their bodies, primarily internal organs and not muscle. The CT DPH advises eating fish from water bodies with blooms in moderation (1 - 2 meals/week). Remove skin and internal organs before cooking and wash fillets before cooking and freezing.Current Classification of Cyanobacteria Blooms and What You Can Do

The CT DPH advises local health departments to issue advisories based solely on visual inspection of water clarity and presence of scums. Advisories are posted at public beaches and other access points. Toxin concentrations may not be at dangerous levels even when a scum is observed on the surface, but caution is advised. On the other hand, toxin concentrations can also be at dangerous levels even after a bloom has dispersed and is not directly observed. Therefore, analyzing water for toxin concentrations is warranted and must be performed by a certified analytical laboratory. It is important to monitor on a regular basis.

When there is a green scum built-up on the surface of the water it is too late to slow down the growth of the bloom. Scum indicates that there is an algal bloom fully present but, we do not know how severe or toxic it may be until the water is tested. Visually, something is happening, but we do not know quantitatively how many toxins are in the water or what species of cyanobacteria they come from. The goal is to apply treatments to the water before a bloom is fully mobilized. For treatment and management information please go to our Taking Action page.

People Matter, Here's What You Can Do

As a bloom develops, the lake's water color and clarity changes (Figure 6). If you can see the water quality changing, take extra precaution before entering it.

Figure 6: Blue water is healthy and no precaution is needed where as, blue-green water should be avoided. When the water is slightly blue-green mobilization is gradually occurring and when it is mainly blue-green cyanobacteria are completely mobile and active; do not go in the water at this time.